/******* 客户端程序  client.c ************/
#include <stdlib.h>
#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <unistd.h>
#include <netdb.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <sys/types.h>
#include <arpa/inet.h>

int main(int argc, char *argv[])
{
    int sockfd;
    char buffer[1024];
    struct sockaddr_in server_addr;
    struct hostent *host;
    int portnumber,nbytes;

    if(argc!=3)
    {
        fprintf(stderr,"Usage:%s hostname portnumber\a\n",argv[0]);
        exit(1);
    }

    if((host=gethostbyname(argv[1]))==NULL)
    {
        fprintf(stderr,"Gethostname error\n");
        exit(1);
    }

    if((portnumber=atoi(argv[2]))<0)
    {
        fprintf(stderr,"Usage:%s hostname portnumber\a\n",argv[0]);
        exit(1);
    }

    /* 客户程序开始建立 sockfd描述符  */
    if((sockfd=socket(AF_INET,SOCK_STREAM,0))==-1)
    {
        fprintf(stderr,"Socket Error:%s\a\n",strerror(errno));
        exit(1);
    }

    /* 客户程序填充服务端的资料       */
    bzero(&server_addr,sizeof(server_addr));
    server_addr.sin_family=AF_INET;
    server_addr.sin_port=htons(portnumber);
    server_addr.sin_addr=*((struct in_addr *)host->h_addr);

    /* 客户程序发起连接请求         */ 
    if(connect(sockfd,(struct sockaddr *)(&server_addr),sizeof(struct sockaddr))==-1)
    {
        fprintf(stderr,"Connect Error:%s\a\n",strerror(errno));
        exit(1);
    }

    /* 连接成功了           */
    if((nbytes=read(sockfd,buffer,1024))==-1)
    {
        fprintf(stderr,"Read Error:%s\n",strerror(errno));
        exit(1);
    }
    buffer[nbytes]='\0';
    printf("I have received:%s\n",buffer);
    /* 结束通讯     */
    close(sockfd);
    exit(0);
}

